Hedges: Hedges generally healthy but some brown spots

I recently bought a house in Kelowna and the entire property has a cedar hedge privacy fence around it. They are about 3-4' wide and 10-12' tall.

All of them have decent growth on the tops & the sides and for the most part are a very nice vibrant green. However there are some spots around all of them that vary in size from a foot or so in diameter to 4-5 feet where they are browning from the tips. We irrigate every second day for 40 minutes and I have fertilized them once with a 30-10-10, spraying the entire hedges with a garden hose fertilizer. I really want to keep these hedges healthy, what can I do?

 

They're arborvitae (Thuja occidentalis), not cedar (Cedrus).

Could they have received additional 'watering' from a dog? That's one common cause of brown patches. Otherwise, too much fertiliser can do it too - they are well adapted to low nutrient soils in the wild, so no need to add any fertiliser at all.

 

Thanks for the ID. The brown patches are higher than what the dogs reach. Any suggestions on how to bring them back?